RESPIRATION

THE RESPIRATORY QUOTIENT (RQ)

The rate of CO₂ produced : The rate of O₂ consumed.

C₆H₁₂O₆ + 6O₂ 6CO₂+ 6H₂O   RQ = 6/6 = 1.0

C₁₈H₃₄O₂ + 25.5O₂ 18CO₂ + 17H₂O  RQ = 18/25.5 = 0.7

If photosynthesis is not controlled the RQ can be negative. Therefore, RQ measurements are taken in the dark.

RESPIROMETERS

These measure the rates of respiration in tissues or whole organisms.

KOH or NaOH absorb CO₂

As CO₂ is produced in the respirometer it is absorbed

But at the same time O₂ is absorbed by the organism. This may be absorbed at different rates depending upon the food being consumed.

Two experiments are needed

If glucose is used (b) will show no change (RQ = 1)

If fats are being used a reduced volume will be observed in (b) (RQ = 0.7).

If anaerobic respiration takes place an increase in volume will be observed in (b) (RQ >1)

Therefore: O₂ (in) = Volume change in (a) - Volume change in (b)

Note: Ambient air pressure and temperature need to be controlled as they will also affect the volumes in the respirometer.

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© Paul Billiet 2009